Method and apparatus for supplying measured quantities of a volatile fluid

ABSTRACT

The method and apparatus for controlling the delivery from a source of supply to a point of utilization of accurately measured quantities of volatile fluids, supplied as liquids and delivered as gases wherein a liquid under pressure is fed to a chamber where it remains a liquid under lower pressure and thence to an expansion chamber where the liquid is completely evaporated and maintained as a gas under relatively uniform constant pressure, and from which chamber the gas is delivered in measured quantities as required; heat being supplied to said expansion chamber to ensure evaporation of the liquid and to replace the heat lost through delivery of the gas.

United States Patent [72] Inventors Harold Willids Andersen Oyster Bay;Harold W. Andersen, Laurel Hollow; Charles 11. Harrison, Oyster Bay, allof, N.Y.

Sept. 15, 1969 Aug. 10, 1971 II. W. Andersen Products, Inc.

Oyster Bay, N.Y.

Continuation-impart of application Ser. No. 561,777, June 30, 1966, nowPatent No. 3,516,223.

[21 1 Appl. No. [22] Filed [45] Patented [73] Assignee [54] METHOD ANDAPPARATUS FOR SUPPLYING MEASURED QUANTITIES OF A VOLA'IILE FLUID PrimaryExaminer-Albert W. Davis, Jr. Attorney-Frank .1. Jordan ABSTRACT: Themethod and apparatus for controlling the delivery from a source ofsupply to a point of utilization of accurately measured quantities ofvolatile fluids, supplied as liquids and delivered as gases wherein aliquid under pressure is fed to a chamber where it remains a liquidunder lower pressure and thence to an expansion chamber where the liquidis completely evaporated and maintained as a gas under relativelyuniform constant pressure, and from which chamber the gas is deliveredin measured quantities as required; heat being supplied to saidexpansion chamber to ensure evaporation of the liquid and to replace theheat lost through delivery of the gas.

SWITCH 43 7 PRESSURE (44 45 ssnsnwc 7 I A METHOD AND APPARATUS FORSUPPLYING MEASURED QUANTITIES OF A VOLATILE FLUID This application is acontinuation-in-part of copending application Ser. No. 561,777, now.U.S.Pat. No. 3,516,223 issued June 23, 1970 being directed to specificimprovements in the sterilant supply system applicable to the apparatusdis closed in said application, as well as for other comparablepurposes.

The measurement, packaging, and dividing into uniform dosesof fluidmaterials having low boiling points present great 'difficulties, duelargely to the unlimited expansibility of gases and the importantinterdependent effects of changes in temperature, pressure and volume.It is an object of the present invention to utilize such phenomena iriobtainingextr'emely accurate control of a volatile substance such as asterilant,

thereof, for example) delivered to each package which is processedthrough the system'of said application. After each package, pouch or bagis placed over the torpedo or connecting means, the excess air iswithdrawn from the bag by an external vacuum system. When the air iswithdrawn, thevacuum system is disconnected, and a measured amount ofsterilant is. injected'into the bag-the correct amount varying with thecontents, the size of the bag, and other sterilization parameters.

One method of controlling the amount of sterilant gas ad- 'mitted to thecontainer'being sterilized, is to accurately regulate the pressure'ofthe delivered gas and vary the time it is permitted'to flow into thecontainer. Experience has shown, for example, that a gas deliverypressure'of approximately pounds per inch gage will permit accuratedelivery to the container being sterilized with injection times of l to4 seconds for typical products to-be sterilized. It is readily apparentto one skilled in'the art that increased delivery pressures would mean Ishorter delivery times, and vice versa, for the same amount of gasdelivered. I

separated into two groups. One group is concerned with sterilants, whosephysical parameters are such that the delivery pressure, or the selfpressure of the liquid/gas at room temperature is below the necessary ordesired delivery pressure for which the system is designed. For example,ethylene oxide has a vapor pressureof approximately 7 p.s.i.g. at roomtemperature. In order toraise the-vapor-pressure to approximate ly 20p.s.i.g., heat must be applied to the supply tank or container of theliquid/gas, to raise the temperature of the liquid to approximately 100F. Each delivery of gas to a package withdraws the heat of evaporationof that amount of liquid evaporating within the sterilant supplycontainer to supply the gas withdrawn. This heat must be replaced inorder to maintain the temperature and thus pressure within the tank.

The method of supplying and controlling the required heat pressure, somemethod is necessary to provide the heatof and must be removedfrom thetank only as a liquid under evaporation when-theliquid 'is converted toa gas prior to being injected into the material to be sterilized, as ina machine of the type disclosed in application Ser. No. 56 l ,777.

Ethylene oxide and Freon are completely miscible as liquids.

v the difference in boiling points.

whereby it can be fed in accurately measured quantities to containers orpackages wherein it can be sealed in order to efv such regulators wouldbe prohibitive.

This invention further relates to the method of withdrawing liquids, forexample a sterilant or mixtures of sterilants and inert ingredients, andeffecting the conversion thereof from a liquid to a gas at a controlledpressure. It would be possible to utilize specially constructedregulating/pressure reducing valves to accomplish the pressure reductionand then supplying the heat of evaporation when the liquid is convertedto a gas. It is doubtful, however, that this method would providetheclosc control of the delivery pressure deemed necessary for anaccurate delivery of measured doses of sterilant gas or gas mixture tothe material to be sterilized, and the cost of In the accompanyingdrawings: FIG. 1 is a schematic representation of the controls and otherelements of an apparatus with which the present apparatus may suitablybe associated, corresponding to FIG. 6 of application Ser. No. 561,777;

FIG. 2 represents somewhat diagrammatically, in elevation and partly insection, a form of the apparatus for handling high pressure liquids, and

FIG. 3 is a wiring diagram for the apparatus of FIG. 2.

7 As indicated in FIG. 1, an article sterilizing system may include asterilant source 1, a valve 2 controlling the release of sterilanttherefrom, a torpedo 3 designed for introduction into a receptacle (notshown) for articles to be sterilized, a conduit 4 from valve 2 totorpedo3 and adjustable automatic sensing The control of the gas deliverypressure can conveniently be is the subject of contemporaneously filedapplication Ser. No.

857,802 filed Sept. I6, 1969.

' The second group of sterilants, to the controlof which the presentapplication is directed, includes those which are normally in excess ofthe required delivery pressure when they are stored as a liquid in thecommercial shipping containers. For

and control devices 5, 6, with or without receptacle evacuating means 7,8 and closing and sealing means 9, 10, all as more fully described insaid copending application.

* According to the present invention, provision is made for admittinga'small quantity of liquid to a reservoir tank in a series of impulses.FIG. 2 shows a conventional commercially available storage tank 35filled with a liquid 36 under pressure with a liquid/gas interface 37and gas under pressure above the interface shown generally as 38. Thetank is fitted with a delivery tube 39 whose opening is at the bottom ofthe tank so that when valve 40 is opened, the vapor pressure of the gas38 above the liquid forces the'liquidthrough tube 39 into the,

connecting tube 41. Solenoid valve 42 is controlled by a pressuresensitive switch generally shown as 43. The solenoid valve 42, pressuresensing switch 43 and a chamber 44 of small volume,'communicate througha small orifice 45 with the interior of expansion tank 46. When thepressure switch 43 senses that the pressure in expansion tank 46 isbelow the set point of the pressure switch 43, it energizes the solenoidvalve 42, thus admitting high pressure liquid from the storage tank tothe small volume chamber 44.11 be direct connection to the high pressureof the storage tank instantly activates the pressure sensing switch 43and immediately closes the solenoid valve 42. This quickaction,typically a few milliseconds, admits only a small volume of liquid tochamber 44, in the concept of a pulse. The high pressure liquid inchamber 44 flows into expansion tank 46 through restrictive orifice 45.The size of the orifice 45 and the pressure differential between chamber44 and expansion tank 46 determine the time required for the pressure inchamber 44 to equilibrate with the pressure in expansion tank 46. Whenthe pressure in chamber 44 again reaches the set point of the pressuresensing switch,

anotherpulse of liquid is admitted to said chamber, and subpressureinside tank 46. When the pressure in the tank 46 increases to the setpoint of the pressure switch 43, no further pulses of liquid will beadmitted to chamber 44. However, if gas is withdrawn from expansion tank46, the pressure in tank 46 will decrease. This decrease in pressurewill be transmitted to pressure sensing switch 43 through orifice 45 andchamber.

44. When the pressure decreases to the set point of the pressure sensingswitch, it causes another pulse of liquid to be admitted to theexpansion tank. By proper design of the relative volumes of the chamber44, and expansion tank 46, and selection of the correct orifice size 45,the system can be made to control the pressure in the expansion tankvery closely. For example, using a mixture of 12 percent ethylene oxideand 88 percent Freon, the pressure within the tank, and thus thedelivery pressure to the point of use can be controlled within p.s.i.g.

One problem with conventional pressure sensing switches is thedifferential pressure between the turn on point, and the turnoff point.On commercially available switches, this differential may be as great aspercent of the set point pressure. The present method obviates thisproblem by sensing only the turn on point of the pressure sensing switchto trigger the liquid pulse. The immediate transmittal of high pressurefrom the storage tank far exceeds the differential pressure of thesensing switch.

The expansion tank 46 is fitted with thermostatically controlledheaters, shown generally at 47, to provide the heat of evaporationrequired to convert the liquid to a gas in the expansion tank 46. It isnecessary to provide this additional heat to assure that all of theliquid will be evaporated to the gaseous state. This is particularlytrue where a mixture of liquids is used. For example, where 88-12Freon/ethylene oxide mixture is used, if heat is not supplied to theexpansion tank, it will self-cool due to the evaporation of the liquidmixture to the gaseous mixture. The Freon component will continue toevaporate and self-cool the tank, however, the ethylene oxide componentwill remain as a liquid in the tank, because its condensation point isabove the temperature in the self-cooled tank.

Delivery to the point of use of the gas or gas mixture is achievedthrough conduit means 48 to valve 49 (indicated as valve 2, in FIG. 1).Valve 49 can conveniently be a solenoid valve controlled by an externaltiming mechanism, 5,6 in FIG. 1. Accurate delivery of aliquots of gas orgas mixtures can be obtained by carefully controlling both the deliverypressure by the method described, and the time during which valve 49delivers the gas to the point of utilization.

What we claim is:

1. Apparatus for converting a volatile liquid at a given pressure to agas having a substantially lower pressure and for supplying measuredquantities of said gas to a point of utilization comprising, meansconfining said liquid under pressure, container means including firstand second chambers, conduit means for delivering said liquidintermittently to said first chamber, means operable in said conduitmeans to control the flow of liquid from said confining means to saidfirst chamber in small intermittent doses in response to the lowering ofthe pressure in said first chamber to a set point, a restricted apertureproviding continuous communication between said chambers andconstituting means for passing measured quantities of said liquid tosaid second chamber, means for heating said second chamber to vaporizesaid liquid therein, means for maintaining the temperature of the gasformed by said vaporization at a predetermined level, and means fordelivering measured quantities ofsaid gas to a point of utilization.

2. Apparatus according to claim 1 wherein said operable means comprisesa solenoid valve in said conduit means, and pressure sensing meanscontrolling said solenoid valve as a function ofchanges ofliquidpressure in said first chamber.

3. Apparatus according to claim 1 in which said second chamber issubstantially larger than said first chamber.

4. Apparatus according to claim 1 in which said heating means has thecapacity to supply more heat to the gas in the second chamber than canbe removed by the delivery of gas therefrom.

5. Apparatus according to claim 1 wherein the restriction of saidaperture is such as to cause a substantial pressure drop between saidfirst and second chambers.

6. The method of supplying measured quantities of gas to a point ofutilization which includes, providing a quantity of volatile liquidunder pressure, providing container means having a first chamber and anexpansion chamber connected by a restricted aperture, sensing thepressure of the liquid in said first chamber, feeding small doses ofsaid liquid intermittently to said first chamber under reduced pressurein response to the lowering of the pressure in said first chamber to aset point permitting escape of said liquid continuously through saidrestricted aperture from said first chamber to said expansion chamber,supplying heat to said expansion chamber to ensure complete evaporationof said liquid to gas, and delivering measured quantities of said gas toa point of utilization.

7. The method according to claim 6 in which the interruption of saidfeeding is effected in response to increase of pressure in said firstchamber.

1. Apparatus for converting a volatile liquid at a given pressure to agas having a substantially lower pressure and for supplying measuredquantities of said gas to a point of utilization comprising, meansconfining said liquid under pressure, container means including firstand second chambers, conduit means for delivering said liquidintermittently to said first chamber, means operable in said conduitmeans to control the flow of liquid from said confining means to saidfirst chamber in small intermittent doses in response to the lowering ofthe pressure in said first chamber to a set point, a restricted apertureproviding continuous communication between said chambers andconstituting means for passing measured quantities of said liquid tosaid second chamber, means for heating said second chamber to vaporizesaid liquid therein, means for maintaining the temperature of the gasformed by said vaporization at a predetermined level, and means fordelivering measured quantities of said gas to a point of utilization. 2.Apparatus according to claim 1 wherein said operable means comprises asolenoid valve in said conduit means, and pressure sensing meanscontrolling said solenoid valve as a function of changes of liquidpressure in said first chamber.
 3. Apparatus according to claim 1 inwhich said second chamber is substantially larger than said firstchamber.
 4. Apparatus according to claim 1 in which said heating meanshas the capacity to supply more heat to the gas in the second chamberthan can be removed by the delivery of gas therefrom.
 5. Apparatusaccording to claim 1 wherein the restriction of said aperture is such asto cause a substantial pressure drop between said first and secondchambers.
 6. The method of supplying measured quantities of gas to apoint of utilization which includes, providing a quantity of volatileliquid under pressure, providing container means having a first chamberand an expansion chamber connected by a restricted aperture, sensing thepressure of the liquid in said first chamber, feeding small doses ofsaid liquid intermittently to said first chamber under reduced pressurein response to the lowering of the pressure in said first chamber to aset point, permitting escape of said liquid continuously through saidrestricted aperture from said first chamber to said expansion chamber,supplying heat to said expansion chamber to ensure complete evaporationof said liquid to gas, and delivering measured quantities of said gas toa point of utilization.
 7. The method according to claim 6 in which theinterruption of said feeding is effected in response to increase ofpressure in said first chamber.